Patients considered cetuximab naïve per protocol will be assigned to Scheme 1. The primary purpose of this scheme is to assess the anti-tumor activity of BYL719 in combination with cetuximab (Arm 1) vs. cetuximab as single-agent (Arm 2) in RM HNSCC patients' naïve to cetuximab. Patients in scheme 1 will be randomized in a 2:1 ratio via IRT in two Phase II arms: BYL719 in combination with cetuximab (Arm 1) vs. cetuximab as single-agent (Arm 2). Patients randomized to Arm 2 (cetuximab monotherapy) will have the opportunity to cross-over to combination treatment with BYL719 + cetuximab after experiencing disease progression. Arm 1 will consist of approximately 66 patients and Arm 2 of approximately 33 patients.